Fabrication of degradable lemon-like porous silica nanospheres for pH/redox-responsive drug release

In this work, pH/redox-responsive silica-based nanocarriers were constructed for drug delivery. Lemon-like porous silica (L-pSiO 2 ) sample presents uniform sphere with size of 160–180   nm and processes thiol-functionalized center-radial inner pores and amine-functionalized shell. Cystine (Cys) molecules were conjugated on the surface of L-pSiO 2 to seal the drug-loaded pores. To minimize the premature release, ZnO quantum dots (QDs) were further used to seal the nanopores of pSiO 2 NSs , which could act as gates and fluorescence probes. Both in vitro cellular cytotoxicity and hemolysis assay demonstrated that the L-pSiO 2 /Cys nanospheres (NSs) were highly biocompatible. The L-pSiO 2 /Cys NSs have high specific surface area (201   m 2   g −1 ) and large pore volume (0.426   cm 3   g −1 ) and are suitable to utilize as drug carriers. The DOX-loaded L-pSiO 2 /Cys NSs displayed more efficient cytotoxic to HepG2 cells than free DOX . Both L-pSiO 2 /Cys and L-pSiO 2 /Cys/ZnO carriers displayed low premature and pH/redox-responsive release. The DOX release from L-pSiO 2 /Cys followed the first-order kinetics model with high correlation coefficient. Interestingly, the L-pSiO 2 /Cys carrier displayed GSH-responsive degrading the inner core and pH-responsive dissolving silica shell at physiological environment.